The last day of Tosha Thakkar's life begins very pleasantly, with a leisurely sleep-in after a long late shift at Woolworths the night before.

She's jolted from her half sleep at 10am by the beep of her mobile phone. It's her boyfriend, Ali Syed, a fellow accountancy student at the Sydney campus of Southern Cross University.

She tells Ali she'll rustle up a rice dish for his lunch, jump in the shower and head into the city to meet him at 1pm, at the Bathurst Street convenience store where he works. From there they'll have lunch in Hyde Park before he goes back to work and she sets off for classes in the city. "I'll call you before I leave to catch the train," she says cheerfully.

Tosha was so joyous, so full of life, and she was always so trusting of people.

The pretty 24-year-old Indian with the arresting ebony eyes and jet-black hair pads about her cramped single room, one of only three bedsits in a run-down boarding house above an abandoned nail salon in Croydon, in the city's inner west. Bollywood love songs are soon ringing out from her white laptop, email is dropping into her inbox, and steam is wafting up from her small rice cooker, further warming this windowless space.

Tosha (pronounced 'Too-sha') has added a few modest personal touches (a Persian rug, a cheery yellow bedspread, a small Hindu shrine) to what's otherwise a drab room with burnt orange walls, reflected in sharp relief by a long horizontal mirror spanning one wall.

She's been living here for nearly six months, after arriving in Australia four years earlier on a student visa, and moving between various shared rental digs. Keen to live on her own, she saw an ad for a room in a small boarding house in Edwin Street, Croydon, only five minutes' walk from the railway station, for just $130 a week.

What clinched it for her at the inspection was the security: a steel grille at the end of her floor, and a single entry at the rear of the property, behind a high fence with a padlocked gate, backing on to a quiet laneway.

It's the height of the sweltering summer of 2010-11, the hottest February in NSW in 30 years. Tosha spends most of these humid nights trying to stay cool in her tiny airless room, studying for her last semester, chatting on the phone to her mum, dad and younger brother Dishang in India, or browsing through cosmetic catalogues (she's just become an Avon Lady).

Meanwhile, her next-door neighbour, a short and stocky 19-year-old called Daniel Stani-Reginald, spends hours trawling through web sites on sadistic rapists and serial killers.

Only a makeshift plywood partition divides Tosha's room (unit 2) from Stani-Reginald's (unit 3), but she hears not so much as a beep from next door. Her neighbour has got his headphones plugged into his black laptop while listening to rap artists like Ne-Yo and searching rape terms on Google.

Tosha knows nothing of her neighbour's sadistic online fantasies, but what's worse, mind-numbingly worse, is that she doesn't know he's planning to put them into practice. On the steamy Saturday afternoon of February 12, Stani-Reginald is strolling along the air-conditioned aisles of Target in nearby Burwood, looking for the biggest suitcase he can find.

The following Thursday evening, while Tosha is praying at a Hindu temple in Strathfield, he's repeatedly tapping "body found in suitcase" into Google, returning again and again to the case of a woman in New York, whose raped and strangled body was found in a case.

He's also been stealing his future murder supplies - Stanley knives and plastic cable ties - from his job as a box boy at bathroom supplier Cass Brothers in nearby Petersham, where he spends much of the day sitting at a small desk, slicing open cardboard boxes.

Tosha doesn't know that her neighbour is not long out of jail, that he's got a sexual fetish for Indian girls, that he's got a favoured stomping ground for trying to sexual attacks at knife point, and that he's busted a huge hole in a gyprock wall downstairs, so that he can slip in and out of the empty shop at night, unnoticed.

She hasn't so much as glimpsed inside the teenager's lair, hasn't seen his dumbbells lying on the floor, the line of urine-filled bottles on a shelf.

Tosha occasionally passes him in the corridor, or says hi while she's hanging out her washing in the backyard, but she doesn't even know his name. She confides to a friend at Woollies that there are only two others living with her in the boarding house - an older gentleman called Phillip, and a younger man who, while he's all smiles, stares at her in an unsettling way.

It's been enough to make her buy a small fridge and cooktop for her room, to save her using the communal kitchenette, although she still has to walk past the young man's room to reach the shared bathroom. "Get out of there," a friend tells her.

But she already has a new flat lined up, and will be moving out soon anyway. By June she'll have finished her degree and will apply for permanent residency in Australia. She reassures her friend the creepy gazer is "just a boy".

A week or so later, on an overcast Tuesday in March, this "boy" does her a good turn. She's locked herself out of her room and Stani-Reginald grabs a ladder, clambers over the partition - there's a 20-centimetre gap between the wall over her front door and the ceiling - and unlatches the door from inside.

It's been a tough couple of days for Tosha - she'd come home crying the night before after being reprimanded for being late to work - and her boyfriend, Ali, who's with her, thanks the obliging neighbour.

The smiling Stani-Reginald, who knows Tosha's name from a piece of misdirected mail to his unit, returns to his room, sits with his laptop, and again misuses Google to research crimes. Later, while Tosha is doing the late shift at Woollies in Surry Hills, he spends hours meticulously researching how to clean up a crime scene, what happens in the first 48 hours of a homicide investigation and the legal defences of serial killers. Tomorrow is the day, he decides.

On the last morning of Tosha's life, Wednesday, March 9, 2011, Stani-Reginald is up early. While Tosha sleeps peacefully on the other side of the plywood wall, he neatly tucks in his bed sheets, wolfs down a big bowl of Weet-Bix, pops into his local chemist to buy a packet of Vicks cough drops and at 8.15am phones Cass Brothers to say he's feeling crook.

By the time Tosha receives the wake-up call from Ali, Stani-Reginald has been on the net for 90 minutes, preparing himself.

Next door, Tosha clicks on a selection of Hindi pop music on her laptop. It's 11.48am and she grabs her maroon nightie, which she normally wears between her room and the bathroom, and takes the 12 steps to the shower.

In a lightning stroke, as she's leaving the bathroom some minutes later, Stani-Reginald grabs Tosha, twists an antenna chord around her neck, drags her back to her room, and pulls the door bolt over.

A gold medallist in judo, Tosha puts up a brave fight, desperately clawing at the thick cord around her neck to try and prevent the terrible attack. Tosha's mobile rings again and again. It's Ali, wondering why his beloved hasn't called.

Around 25 minutes into the awful assault, footsteps are heard moving down the hallway outside. It's neighbour Phillip Culbert, home early from his pre-dawn shift as a forklift driver at Flemington markets. But seconds later his door quietly snaps shut. All hope is now gone.

After nearly an hour - when the young woman whom her mum and dad refer to as their "sweet fairy" is dead - Stani-Reginald squeezes her tiny 53-kilogram frame into the black suitcase he's purchased.

At 12.54pm, Stani-Reginald phones Premier Taxis, arranging a cab to pick him up in 10 minutes' time in front of Mario's Pizzeria around the corner. His destination is Meadowbank Park, an area he knows very well. On his way out the door, he bangs the heavy suitcase against a chair in the hallway, but he has little trouble getting it down the flight of stairs and wheeling it along the back laneway, around into Edwin Street.

"Jeez, mate, what have you got inside this bag?" the taxi driver asks, grabbing the suitcase from Stani-Reginald, and heaving it into the boot.

Sitting in the front seat, Stani-Reginald swigs from a one-litre water bottle he always carries with him, fusses with his phone and asks the taxi driver chirpily how his day has been. After being dropped off, he doesn't so much as squint in the fierce early afternoon sun as he drags the wheeled suitcase along a concrete pathway into Meadowbank Park, following the course of a stormwater canal.

When he finds a spot free of shrubbery, he lifts the heavy suitcase over a wire fence into the canal - oblivious to being seen by a group of workmen fixing a gas pipeline on a bridge nearby - and watches as the suitcase is swallowed up by the brown tongue of water feeding into the Parramatta River.

Now ravenous, Stani-Reginald makes his way to Rhodes shopping centre, buys a sandwich at Subway, and does a spot of window shopping in Dick Smith before catching another taxi back to Ashfield station. From there he catches a train home to Croydon, no doubt imagining the suitcase, driven by the strong current in the stormwater canal, resting on the bottom of the Parramatta River.

Meanwhile, across town, Ali Syed is growing anxious. The girl he's been seeing for just under a year, the girl he dreams of marrying, isn't answering his calls. At 2pm, he leaves work, jumps in his car and drives to Croydon, pulling up in the laneway behind the boarding house. After scaling the 10 steps to the second floor, he hears music ringing out from Tosha's room, and pushes open her unlocked door.

What he is confronted with mystifies him. Tosha's handbag, purse and phone are sitting on the bed. Her mobile is flashing with 26 missed calls from him and her friends. Her damp bath towel lies crumpled near the door, next to the thongs she wears to the bathroom, although they're oddly positioned. The rice cooker is filled with steamed rice. There is just one thing missing from her rickety wardrobe, it dawns on him. Tosha's sleeveless maroon nightie, which he knows she wears to the bathroom.

After ringing around friends to establish if they've seen Tosha and coming up with nothing, Ali calls 000 and reports a missing person. Mutual friends arrive and start fanning out through the local streets, searching for their friend.

Then, in the late afternoon, while he's zig zagging from shop to shop near Croydon station, asking everyone if they've seen his girlfriend, Ali walks straight into Stani-Reginald. "Did you see the girl who lives next door to you?" asks Ali, searching Stani-Reginald's face. "She's been missing since 11am".

"No, man," replies Stani-Reginald.

"I work at Cass Brothers as a plumber ... I leave at 8am and get home at 5pm."

"Did you happen to see her this morning when you were leaving?"

"No."

Ali notices a red stain on Stani-Reginald's tongue. "What's that?"

"I've just had an ice-cream. Just chilling out after work." They shake hands and Ali continues his desperate search.

That evening, after the police knock on Stani-Reginald's door with enquiries into the missing girl (he only saw her "yesterday morning", he tells them), and after he's carried his bag of clothes to the laundromat and passed Tosha's worried friends on the back steps, Stani-Reginald logs on to his laptop. He punches "beginnings of a serial killer" into Google.

Tosha remains a missing person for just 48 hours. On Friday morning, while Stani-Reginald is at work, the flow in the stormwater canal drops back so much that the suitcase, snagged on a tree branch near the junction to the Parramatta River, pokes out of the water.

A curious young Irish labourer, one of the four men who saw Stani-Reginald push the case into the canal two days earlier, tosses a rope out and drags the bag to shore, imagining it might contain money or drugs. Using his Swiss army knife, he cuts into a corner of the bag and is confronted with a ghastly sight. A human toe with a painted purple toenail. His work mates call the cops.

Late that afternoon, while Tosha's first cousin Nadali is on her way to Glebe morgue to identify the body, Stani-Reginald arrives home to find police guarding the boarding house. He's escorted to his room and is told not to touch anything in the hallway because they're fingerprinting. He closes the door, opens his laptop, and types "true sociopath" into Google, before browsing a news site about an unknown body discovered in a canal in Meadowbank Park.

The identity of this mystery body is still his dark little secret - or so he imagines. Little does he know that, as late afternoon darkens into evening, as he catches a train to Burwood to patronise a brothel, as he returns to the boarding house to find he's refused access to his room, as he books into the Phillip Street Lodge in Ashfield for the night, he is being watched by the police.

They are led by three detectives determined to get this killer off the streets before he strikes again.

Cars dangling from the upper floors of buildings. The twisted hull of a fishing trawler perched in a downtown street. As the dire images of Japan's quake- and tsunami-stricken north-eastern coast flash across Phillip Culbert's TV in unit 1 on the Saturday morning of March 12, his attention is suddenly fixed on a news ticker running along the bottom of the screen, "Missing Girl's Body Found in Suitcase at Meadowbank Park", with a photo of Tosha.

It's 7.30am, and no sooner has Culbert absorbed the terrible information that his neighbour has been murdered than there's hullabaloo in the corridor outside. He opens his front door to be faced with a scene straight out of CSI: big blue lights, cameras, and forensic police in white space suits.

"So the body has been found," he says to one young female officer.

"Yes, didn't anybody tell you?"

"No, no one told me nothing."

Culbert glances around. Stani-Reginald is nowhere to be seen, and forensic investigators are filing out of his room with his black laptop and a block of kitchen knives, both sealed up in plastic bags. It hits him with a thunderbolt that Daniel is the murder suspect, and has probably been arrested or is on the run. One detective appears engrossed by a carpet stain outside Tosha's doorway.

"What's this?" he asks, before requesting that a square of carpet be cut out. My God, muses Culbert, was Daniel prowling the hallway at night when they were asleep, maybe, you know ... outside Tosha's room?

Even now, three years to the week after the murder of his former neighbour, Culbert, 59, feels a shiver running down his spine as he recalls the events of that Saturday morning, as he struggled to absorb all the shocking news. "It all seemed so unreal," recalls the father of two, sipping on a glass of water in the weatherboard house he now shares with his 26-year-old son in Sydney's south-west.

But what continues to haunt Culbert most is that he arrived home when Tosha was in her death throes. "I normally walked in the door at 2pm, but on that day it was 12.30pm because I was working a new shift," he explains. "I could hear Hindi music coming from Tosha's room, louder than usual, the light was on, and I just presumed she was in there with Ali, because he'd been coming over a lot more recently."

Culbert, who has a daughter Tosha's age, felt protective of the 24-year-old girl. "I always made sure the doors were locked as I left for work in the early morning, but all I was doing was locking her in with this piece of shit."

Culbert leans forward. "I've always fancied I'm pretty good at reading people; I never suspected Daniel because he seemed such a quiet, nice guy. I'd see him occasionally when I went out for a smoke in the backyard, and I'd ask, 'How's it goin', mate?' He told me he was Fijian, which I later found out was a lie, and he was a storeman at Cass Brothers. I suggested he get his forklift licence."

Stani-Reginald was arrested by detectives Trent Power and Peter Rudens at 11pm on Friday night, March, 11 2011, at the Phillip Lodge Hotel, just two days after the murder. His mobile was confiscated and he was interrogated at Campsie police station until 3am.

"What struck us was his icy calmness and absolute politeness, something I don't think I've ever seen in a killer before," says the tall, square-jawed Power. "You could tell he was holding the aggression in, though."

CCTV footage from the taxi, Mario's Pizzeria, Rhodes shopping centre and Ashfield station proved crucial in pinning Stani-Reginald to the crime.

"I remember meeting the technician at the vehicle holding yard and looking over his shoulder as he downloaded the footage from the taxi," recalls Smithers.

"When I saw Stani-Reginald wheeling the same suitcase that contained the body of Tosha, I couldn't believe my eyes. I knew we had him at that point."

When the data from Stani-Reginald's laptop was downloaded byte by painstaking byte, a bright light was shone on the murderer's heart of darkness. Over six months, he had logged nearly 9000 searches about serial killers and rape, how to remove forensic evidence and court cases involving multiple murder. The killer had done his homework.

Stani-Reginald's trademark calmness only showed signs of cracking when Power and Rudens visited him weeks later at Silverwater Jail to show him the CCTV footage of him carrying the black suitcase. "His eyes suddenly opened up wide," Rudens declares, "like ... er ..."

Like what, I ask? Rudens obligingly tries to duplicate the expression, by puffing up his cheeks, bulging his eyes, and turning turkey red. "It was like the real him was about to burst out," he explains. "Under the self-control, this roiling rage ..."

A Tamil refugee from Sri Lanka, Stani-Reginald was brought to Australia when he was about three. When he was just nine years old, his father murdered his mother in their Sydney home (his father, Joseph, who was released after serving 12 years, did not turn up to his son's sentencing hearings).

However, two psychiatric assessments undertaken before the trial showed that Stani-Reginald showed no evidence of a mental disorder or psychosis. In her psychiatric assessment, Dr Yvonne Skinner concluded that "he has shown no capacity for empathy and no signs of remorse".

Thanks to a first-class police investigation and Crown prosecution, led by Mark Tedeschi, QC, and ably assisted by lawyer Rossi Kotsis, who devoted nearly a year to assembling a watertight case against Stani-Reginald, the accused was found guilty of murder and sexual assault.

Although Mark Tedeschi urged the judge to impose a life sentence without parole on Stani-Reginald, arguing he was capable of seeking notoriety as a serial killer, Justice Derek Price sentenced him to 45 years, with a non-parole period of 30 years. This means he could be back on the streets before he turns 50.

In April last year, Stani-Reginald sat stoney-faced in the court room before 20 friends and family members of Tosha as he was sentenced. Justice Price said while there was a high chance the killer would commit more crimes, he didn't "deserve to spend the rest of his life in jail".

Meanwhile, Tosha's family is left with never-ending grief. Dishang Thakkar wipes back tears during a Skype interview from his family's home in Vadodara city in western India as he recalls his big sister, a natural joker.

"She was so joyous, so full of life," he says, "and was always so trusting of people." Dishang compares his loss to that of an open wound that will never heal. His parents' health and happiness, he adds, have been ruined.

Tosha's boyfriend, Ali Syed, was inconsolable, and left his studies and life in Australia for travel overseas. He has lost contact with many of his friends.

Among the drab shops lining Edwin Street, the faded pink door of the empty nail salon looks much the same as it did when Tosha and Stani-Reginald lived here, except that the boarding house above it has been internally gutted. On the day Good Weekend visits, accompanied by former resident Phillip Culbert, we come across a poignant sight: a pile of Tosha's and Stani-Reginald's belongings, tossed into a pile in the backyard with other rubbish. Tosha's Persian rug, rice cooker and Avon bag sit at the top, near water-damaged bills for Stani-Reginald.

As Culbert forlornly picks up Tosha's Avon bag and dusts it off, I'm reminded that tragedies like this one can only be fully understood by those closest to them. Parents. Siblings. Partners. Dear friends.

As they live through the horror of the crime and its aftermath, as they follow the case through every nerve-shattering step in the courts, every agonising detail of the atrocity against their loved one is forever etched in their minds. They know so much more than the prosecution and defence. More than the judges. And certainly more than journalists.

Then I recall something one of Tosha's cousins put to me over lunch some weeks earlier. Given its highly detailed planning and execution, was this really Stani-Reginald's first kill? What if he wasn't a wannabe serial killer at all, what if he'd struck earlier? Stani-Reginald always excelled in keeping secrets.